Re: [PATCH 04/21] Generic percpu refcounting

[Kent Overstreet]

On Tue, May 14, 2013 at 03:51:01PM +0200, Oleg Nesterov wrote:
> On 05/13, Kent Overstreet wrote:
> >
> > +int percpu_ref_kill(struct percpu_ref *ref)
> > +{
> > +	unsigned __percpu *pcpu_count;
> > +	unsigned __percpu *old;
> > +	unsigned count = 0;
> > +	int cpu;
> > +
> > +	pcpu_count = ACCESS_ONCE(ref->pcpu_count);
> > +
> > +	do {
> > +		if (!pcpu_count)
> > +			return 0;
> > +
> > +		old = pcpu_count;
> > +		pcpu_count = cmpxchg(&ref->pcpu_count, old, NULL);
> > +	} while (pcpu_count != old);
> 
> This is purely cosmetic, feel free to ignore. But afaics all we
> need is
> 
> 	pcpu_count = ACCESS_ONCE(ref->pcpu_count);
> 	if (!cmpxchg(&ref->pcpu_count, pcpu_count, NULL))
> 		return 0;

Whoops, yep. I was ripping out the dynamic stuff from my dynamic percpu
refcount code and missed that bit.
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